public class T {
}


 class ListNode {
      int val;
      ListNode next;
      ListNode(int x) {
         val = x;
          next = null;
     }
  }

 class Solution {
     public boolean hasCycle(ListNode head) {
         if (head == null || head.next == null) {
             return false;
         }
         ListNode fast = head.next.next;
         ListNode slow = head;

         while (fast != null && fast.next != null) {
             if (fast == slow) {
                 return true;
             }


             fast = fast.next.next;
             slow = slow.next;
         }

         return false;


     }
 }
